共查询到20条相似文献,搜索用时 15 毫秒
1.
液晶的转动粘质系数的测试原理与方法 总被引:1,自引:1,他引:0
液晶的转动粘质度是液晶用于显示和通讯的重要物理参量.本文设计开发了基于微机的液晶参数测试光学系统,在该系统上研究了液晶的转动粘质系数的测试原理与方法:通过测试液晶盒在偏置电压下相位驰预时间,推导出转动粘质系数的值.测试Merck公司的 E7液晶的转动粘质系数随温度变化的曲线,进行了理论拟合,测试结果与理论符合得很好.通过分析另一系统对液晶介质常数随温度变化的曲线的测试结果,验证了该测试原理与方法的正确性.该测试方法具有简单、自动化的特点. 相似文献
2.
Hydrodynamics of planar nematic liquid crystal molecules under the influence of horizontal pressure gradient was studied, theoretically. The pressure gradient is due to nematic liquid crystal volume expansion which is a consequence of the incompressibility of the liquid. The resulting director reorientation which is due to coupling between the director orientation and fluidity of the liquid is calculated numerically for the hard and weak anchoring conditions at the cell walls. 相似文献
3.
We present a molecular dynamics study of reentrant nematic phases using the Gay-Berne-Kihara model of a liquid crystal in nanoconfinement. At densities above those characteristic of smectic A phases, reentrant nematic phases form that are characterized by a large value of the nematic order parameter S?1. Along the nematic director these "supernematic" phases exhibit a remarkably high self-diffusivity, which exceeds that for ordinary, lower-density nematic phases by an order of magnitude. Enhancement of self-diffusivity is attributed to a decrease of rotational configurational entropy in confinement. Recent developments in the pulsed field gradient NMR technique are shown to provide favorable conditions for an experimental confirmation of our simulations. 相似文献
4.
We investigated dielectric properties of a hockey-stick-shaped liquid crystal (HLC). Two dielectric relaxation modes were observed at 0.91 kHz and 4.51 MHz. The low frequency relaxation modes in isotropic, smectic, and nematic phases are related to the motion of ions, collective tilt fluctuation, and rotation around the long molecular axis, respectively. Meanwhile, the high frequency relaxation modes in nematic and smectic phases was due to the rotation around the short axis of the molecules and hindered by the resistance of the ITO layers. We also examined the electrooptical response of the 5.0 wt% HLC-doped commercial nematic liquid crystal (LC) mixtures. The birefringence of the LC mixture was slightly increased, while the falling time and the rotational viscosity was decreased in the nematic phase. 相似文献
5.
The system of equations describing the thermal orientation effect in nonchiral liquid crystals, which was observed earlier,
is proposed and substantiated. The effect of the director reorientation under the action of the temperature gradient is in
many ways analogous to the Freedericksz transition in electric or magnetic fields. The angle of deviation of the director
from the initial position is determined by the square of the temperature gradient. The effect is observed for a nematic liquid
crystal, initially uniformly oriented, and is not accompanied by macroscopic fluxes of the medium under stationary conditions. 相似文献
6.
The effective rotational viscosity and polar anchoring coefficient of a nematic liquid crystal were determined using electro-optical response by changing the frequency of the electric field in the kilohertz range. Both quantities monotonically decreased with an increase in the frequency and converged to a certain value at several tens of kilohertz. The effective rotational viscosity changes more than the order of magnitude in experimental range. On the other hand, the effective value of anchoring coefficient changes several times. We tried to explain the trends with the effect of an electric field induced by the motion of ionic impurity in liquid crystal. 相似文献
7.
向列相液晶动态全息存储特性的研究 总被引:6,自引:6,他引:0
研究了C60掺杂向列相液晶中全息光栅的形成, 实验中我们利用了一种特殊的全息再现方法:即低电压记录, 高电压再现, 观察到清晰的全息再现像. 实验结果表明样品具有良好的全息存储能力. 分析了电压对实验结果的影响, 实验表明:为了避免动态散射的出现应使用较低的记录电压, 而再现时应采取高电压以重新激发隐藏的光栅, 提高再现的质量. 相似文献
8.
9.
10.
11.
H. Gruler U. Dewald M. Eberhardt 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(1):187-192
Interacting cells have the ability to form liquid crystal phases: (i) A cluster of a polar nematic liquid crystal is formed
by cells which emit molecules for attracting other cells and (ii) an apolar nematic liquid crystal is formed by elongated
cells which have an anisotropic steric repulsion. The angle distribution function is predicted by using the characteristics
of an automatic controller where the extracellular guiding field is approximated by two-dimensional mean-field. The nematic
liquid crystal state is quite well described by the model.
Received 7 September 1998 and Received in final form 4 March 1999 相似文献
12.
N. M. Shtykov M. I. Barnik L. M. Blinov B. A. Umanskii S. P. Palto 《JETP Letters》2007,85(12):602-604
The amplification of the emission of a microlaser based on a cholesteric liquid crystal by means of a uniformly oriented layer of a laser-dye-doped nematic liquid crystal is demonstrated. The nematic liquid crystal is characterized by the anisotropy of optical properties, including the amplification coefficient, which opens the possibility of creating amplifiers controlled by a low electric field. 相似文献
13.
Chen-Yang Liu 《Physics letters. A》2008,372(31):5198-5202
Photonic crystals (PCs) have many potential applications because of their ability to control light-wave propagation. We have investigated the tunable absolute bandgap in a two-dimensional anisotropic photonic crystal structures modulated by a nematic liquid crystal. The PC structure composed of an anisotropic-dielectric cylinder in the liquid crystal medium is studied by solving Maxwell's equations using the plane wave expansion method. The photonic band structures are found to exhibit absolute bandgaps for the square and triangular lattices. Numerical simulations show that the absolute bandgaps can be continuously tuned in the square and triangular lattices consisting of anisotropic-dielectric cylinders by infiltrating nematic liquid crystals. Such a mechanism of bandgap adjustment should open up a new application for designing components in photonic integrated circuits. 相似文献
14.
The self-asymmetrization of dynamic phase grating profile in a model medium with properties of nematic liquid crystal, caused
by the internal electric field induced in this medium, has been numerically simulated. 相似文献
15.
Vinyltriethoxysilane based inorganic–organic glasses dispersed with 4′-n-pentyl-4-cyanobiphenyl nematic liquid crystal are designed to fabricate a new type of gel glass dispersed with liquid crystal. Scanning electron microscopy shows that the nematic liquid crystal phase, occupying the interconnected cavities, is continuously embedded in the inorganic–organic matrixes. The effect of the nematic liquid crystal weight concentration on the morphology is investigated. The differential scanning calorimetry shows that the nematic-isotropic transition temperature depends on the nematic liquid crystal weight concentration. The Raman spectra show that there are no obvious Raman frequency shifts, compared with pure nematic liquid crystal. The in situ diffuse reflectance FTIR spectra show that the integral intensity of bands of hydroxyls has not varied. 相似文献
16.
We derive expressions for the order parameter dependence of the viscosity coefficients of a biaxial nematic liquid crystal
by comparing its dissipation function expressed in terms of directors with that expressed in terms of order tensors. The results
enable us to identify the dominant flow viscosity coefficients and to compare their temperature variation according to their
dependence on the dominant scalar order parameters. By considering different orientations of an external field, we identify
three characteristic switching times corresponding to three rotational viscosities, and we estimate the ratio of the switching
times of the primary and the secondary directors. 相似文献
17.
An electron nematic is a translationally invariant state which spontaneously breaks the discrete rotational symmetry of a host crystal. In a clean square lattice, the electron nematic has two preferred orientations, while dopant disorder favors one or the other orientations locally. In this way, the electron nematic in a host crystal maps to the random field Ising model. Since the electron nematic has anisotropic conductivity, we associate each Ising configuration with a resistor network and use what is known about the random field Ising model to predict new ways to test for local electronic nematic order (nematicity) using noise and hysteresis. In particular, we have uncovered a remarkably robust linear relation between the orientational order and the resistance anisotropy which holds over a wide range of circumstances. 相似文献
18.
A. L. Alexe-Ionescu 《Il Nuovo Cimento D》1993,15(12):1489-1506
Summary The elastic deformations in nematic liquid crystals are analysed in one and two dimensions. The influence of the flexoelectric
polarization on the elastic properties of the medium is studied. It is shown that for one-dimensional deformations, the presence
of the flexoelectric polarization introduces a renormalization of the elastic constants. On the contrary in the bidimensional
case, the effect of the flexoelectricity is not a simple renormalization of the elastic constants. The profiles of the electric
potential and of the tilt angle are evaluated for the cases in which the substrate is an insulating or conducting material.
The validity of the calculations is discussed by considering the value of Debye's screening length of the nematic liquid crystal. 相似文献
19.
M. R. Hakobyan R. S. Hakobyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2011,46(3):116-118
We show that magnetic colloids could increase the coupling of a liquid crystal to a week magnetic field. Magnetic Fréedericksz transition in a planarly oriented nematic liquid crystal doped with spherical ferromagnetic nanoparticles is considered theoretically. It is shown that even spherical nanoparticles could decrease a threshold of this transition because they strongly increase the magnetic field in the medium. This phenomenon indicates the possibility to use the considered system in magneto-optical displays. 相似文献
20.
The properties of localized electromagnetic modes in a one-dimensional photonic crystal with a structural defect layer were studied. The role of the defect was played by an anisotropic nematic liquid crystal layer. The frequency and the damping factor of defect modes were shown to substantially depend on the defect layer thickness and the orientation of the optical axis of the nematic. The transmission spectra of photonic crystals with one and two lattice defects were studied. Taking into account the special feature of nematic liquid crystals distinguishing them from usual crystals, namely, large permittivity anisotropy, it was shown that the transmission spectrum of the photonic crystal could be controlled by varying the orientation of the optical axis of the nematic, for instance, under the action of an external electric field. 相似文献